Light incident angle controllable electronic device and manufacturing method thereof

ABSTRACT

Disclosed herein is a method of changing characteristics of an electronic device, including the steps of: applying light to an electronic device through a plurality of media having different refractive indexes from each other, the electrical characteristics of the electronic device being changed depending on the amount of incident light; and changing an incident angle of light applied the electronic device to adjust the amount of incident light. There is provided a method of providing light incident angle dependency by a simple procedure of accumulating additional media in various electronic devices. In the method, the light incident angle selectivity of the electronic device can be maintained even when the inclination angle of the device is changed depending on the axis parallel to the incident direction of light even though the incident direction thereof is fixed. This means that the performance of the device can be controlled only by changing the inclination angle of the device without greatly changing the dynamic state of the device. Further, since the movement speed of photons is higher than that of electrons and the signal interference of photons is lower than that of electrons, an additional effect of increasing the operating speed of the device or decreasing the size of the device can be expected.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.14/465,378, filed Aug. 21, 2014, which claims priority to Korean PatentApplication No. 10-2013-013340, filed Nov. 5, 2013, each of which isincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to a light incident angle controllableelectronic device and a manufacturing method thereof. More particularly,the present invention relates to an electronic device, the electricalcharacteristics of which are changed depending on the incident angle ofincoming light, and to a manufacturing method thereof.

2. Description of the Related Art

The common problem with various electronic products as necessities ofmodern society is that information transmission is basically induced byelectrical stimulation, that is, electron migration. However, with adecrease in the size of an electronic device, the physical positionbetween two transmission lines becomes closer, whereas signals aredamaged or distorted by strong interaction between electrons, thuscausing an electrical signal interference problem and lowering systemefficiency. In order to solve this problem, when light, which issuperior in terms of high movement speed, noninterferencecharacteristics, parallel movement characteristics, high integrationeasiness and the like, is used, it is expected to offer a novelinformation processing method using photoelectric signals. Here,particularly, when a semiconductor circuit recognizing the irradiationdirection of photoelectric signals and exhibiting two differentelectrical characteristics according the direction thereof is realized,it will become a motive power for opening a motion-controllablehigh-technology age. In order to recognize data and process informationusing light, it is required to develop a method of converting light intooptical information and transmitting the optical information as well asa method of freely controlling the flow of light. However, it takes alot of time to develop such technology or equipment. Therefore, a methodof making up for the weak points in an electronic informationtransmission system without changing the structure of an electronicdevice is required.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been devised to solve theabove-mentioned problems, and an object of the present invention is toprovide a method of allowing an electronic device to have light incidentangle selectivity.

Another object of the present invention is to provide a novel electronicdevice having light incident angle selectivity.

In order to accomplish the above object, an aspect of the presentinvention provides a method of changing characteristics of an electronicdevice, including the steps of: applying light to an electronic devicethrough a plurality of media having different refractive indexes fromeach other, the electrical characteristics of the electronic devicebeing changed depending on the amount of incident light; and changing anincident angle of light applied to the electronic device to adjust theamount of incident light.

In the present invention, a first medium having a first refractive indexis disposed on the surface of the electronic device, and the lightpenetrates a second medium having a second refractive index larger thanthat of the first refractive index and then penetrates the first mediumdisposed on the surface of the electronic device to allow the light tobe applied to the electronic device, whereby the amount of the light ischanged depending on the change in the incident angle of the light.Preferably, the refractive index of the first medium disposed on thesurface of the electronic device may be lower than that of the secondmedium.

In an embodiment of the present invention, in order to allow theelectronic device to exhibit total reflection as an extreme refractioncharacteristic, it is preferred that a first medium having low opticaldensity be disposed on the electronic device and a second medium havinghigh optical density be disposed on the first medium. The light appliedfrom a light source to the second medium is refracted ortotally-reflected at the interface between the two media, thuscontrolling the amount of light reaching the electronic device. Thelight source may be disposed in the air over the second medium, but,preferably, may be disposed in the second medium in consideration ofattenuation and absorption characteristics of light.

In the present invention, with the intention of total reflection as anextreme refraction characteristic, the structure of a medium may belimited depending on optical density, but is not limited thereto.Further, the arrangement of the first and second media may be relativelydifferent. The two media may be solid media, but liquid or gas media maybe arranged on the electronic device in order to reversibly change anarrangement structure. When the two media are not solid media, it isdifficult for a medium having high optical density to be naturallydisposed on a medium having low optical density because optical densityis generally in proportion to mass density. In order to solve thisproblem, it is preferred to form the two fluidic media into stableboundary and structure using a superhydrophobic surface treatment. Asuperhydrophobic surface, on which water does not adhere or weaklyadheres, may be configured in the following order on an electronicdevice: air (first medium) and water (second medium) from the bottom,because it tends to possess an air layer between the surface and a waterlayer when it is immersed into water. Here, this air layer provides anenvironment for protecting the electronic device and connector not beingsealed with an insulator and the electrode wiring connecting devicesfrom water to stably operate the electronic device.

In the present invention, the first medium may include gas, preferablyoxygen that can control the oxidation state of the electronic device,and more preferably air that can be used at low cost.

In the present invention, preferably, the first medium may be atransparent superhydrophobic layer including gas having a low refractiveindex. A superhydrophobic surface can be generally obtained by thecombination of high surface roughness and chemical coating for offeringwater repellency. Nanofibers have structural characteristics ofincreasing optical reactivity and physical characteristics of providinga superhydrophobic surface. The transparent superhydrophobic layer maybe formed by accumulating air between nanostructures treated with fattyacid, an SAM material or a compound having low surface energy such as afluorine compound.

In an embodiment of the present invention, the fluorine resin, which isa material for superhydrophobic surface treatment, is advantageous inthat it has low surface energy, does not exert an influence on theelectrical characteristics of the electronic device, does notdeteriorate transparency, and is not damaged by optical stimulation. Thefluorine resin may bepoly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene].The chemical coating of the material for superhydrophobic surfacetreatment may be easily performed by applying the fluorine resin ontothe nanostructured device using spin coating.

In the present invention, the nanostructure is a nanowire, nanotube ornanorod disposed on the surface of the electronic device. Preferably,the nanostructure may be a nanowire vertically grown on the surface ofthe electronic device. The nanostructure may be made of various kinds ofoxides. Examples of the oxides may include Al₂O₃, SiO₂, TiO₂, VO, VO₂,V₂O₃, V₂O₅, MnO, MnO₂, FeO, Fe₂O₃, Fe₃O₄, CoO, Co₂O₃, Co₃O₄, NiO, CuO,Cu₂O, Y₂O₃, ZrO₂, NbO, NbO₂, Nb₂O₅, MoO₂, MoO₃, RuO₂, PdO, AgO, CdO,In₂O₃, SnO, SnO₂, Sb₂O₃, Sb₂O₅, HfO₂, Ta₂O₅, WO₃, IrO₂, NiO, NO, N₂O andMgO.

In the present invention, more preferably, the nanostructure may be madeof zinc oxide. Zinc oxide can be easily synthesized into large-areananostructures at low temperature. Further, this zinc oxidenanostructure exhibits resistance variation characteristics in terms ofinformation processing and stability because the digital states “0” and“1” can be maintained for a long time when it is applied to a memorydevice.

In the present invention, the nanostructure, preferably a zinc oxidenanofiber, and more preferably, a zinc oxide nanowire, can be directlygrown using each part of the electronic device as a seed layer. For thepurpose of vertically-aligned growth of the nanostructure, a seed layerhaving a nanometer scale thickness may be famed on the surface of theelectronic device before the formation of the nanostructure. The seedlayer may be formed on a buffer layer by chemical deposition,sputtering, evaporation or a sol-gel process. Here, the materialconstituting the buffer layer may be selected from among Zn, Au, Ag,ZnO, GaN, SiC and TiN, but is not limited thereto. Preferably, the seedlayer may be a zinc oxide thin film or an aluminum-doped zinc oxide thinfilm.

When a nanofiber is formed on the electronic device, the electronicdevice can obtain light incident angle selectivity. However, preferably,when the electronic device is configured in the form of a nanofiber,there are advantages in that the integration degree thereof can beimproved, and simultaneously the optical reactivity thereof can bemaximized because of its large specific surface area.

In the present invention, the second medium may have lower opticaldensity than that of the first medium, and may have a higher refractiveindex than that of the first medium. As the second medium, a liquid maybe used. Preferably, as the second medium, a polar liquid, preferablywater, may be used such that water repellency can be realized by acompound having low surface energy.

In the present invention, the light source may be selected from thegroup consisting of an incandescent lamp, a halogen lamp, a dischargelamp and an LED lamp, but is not limited thereto.

In the present invention, the electronic device can exhibit electricalcharacteristics different from each other when light istotally-reflected from the electronic device while changing its incidentangle and when light is incident upon the electronic device whilechanging its incident angle. The amount of light reaching the electronicdevice is changed drastically based on the critical angle at which totalreflection occurs. Since the first medium located at the lower layer ofthe electronic device is directly brought into contact with zinc oxide,it can directly influence the electrical characteristics of zinc oxide.Particularly, oxygen existing in the air layer is easily adsorbed on thesurface of the zinc oxide nanowires constituting the electronic deviceto attract electrons, and exert an influence on the entire surfacelevel. When zinc oxide receives light to cause photo-excitation, oxygenadsorbed on the surface thereof is detached therefrom, and thus theelectrical characteristics of zinc oxide are changed again by thesurface state thereof. Owing to a series of such processes, when lightis applied at an incident angle larger than the critical angle, generalresistor characteristics are exhibited, but, when light is applied at anincident angle smaller than the critical angle, memristorcharacteristics are exhibited.

In the present invention, the incident angle can be changed depending onthe change in location of a light source or the change in gradient ofthe electronic device.

In an embodiment of the present invention, the electronic device, whichis provided on the surface thereof with a transparent hydrophobic layerincluding nanostructures and gas, and the electrical characteristics ofwhich are changed by the amount of incident light, is irradiated withlight, and simultaneously the incident angle of light is changed tototally-reflect or apply the light, thereby realizing thecharacteristics of a resistor and the characteristics of a memristor,respectively. The transparent hydrophobic layer includes: zinc oxidenanowires vertically grown on a zinc oxide thin film to a length of 600nm or less and treated with a fluorine compound; and air collected inlayers between the zinc oxide nanowires. The electronic device isconfigured such that voltage is applied to upper and lower surfaces of alaminate including a transparent indium-doped tin oxide electrode layer,a glass substrate layer and a zinc oxide layer.

Another aspect of the present invention provides an electronic devicehaving light incident angle selectivity, including: a glass substratecoated with a transparent indium-doped tin oxide electrode; a zinc oxidelayer disposed on the glass substrate; a gold electrode patterned on thezinc oxide layer; a hydrophobic electronic device comprising atransparent hydrophobic layer including zinc oxide nanowires grown onthe zinc oxide layer patterned with the gold electrode andsurface-treated with a fluorine compound and air collected in layersbetween the zinc oxide nanowires; a water layer existing on the surfaceof the hydrophobic electronic device; and a light source applying lightto the electronic device, wherein the light applied to the electronicdevice is totally-reflected or applied at a predetermined angle to allowthe electronic device to have light incident angle selectivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a presents photographs showing the difference in wettabilitybetween a surface-treated device and a non-surface-treated device whentheir gradients are changed, and presents photographs showing the mirrorimage characteristics thereof ({circle around (3)}, {circle around(4)}D) attributable to an air layer when the gradient of thesurface-treated device is higher than a critical angle, FIG. 1b showsthe lateral scanning electron microscope (SEM) images of nonowiresexisting on the surface of the device, and FIG. 1c shows the planarscanning electron microscope (SEM) images of nonowires existing on thesurface of the device.

FIG. 2a is a schematic view showing the refraction angle and directionof a light source when a superhydrophobically surface-treated electronicdevice is immersed in water, FIG. 2b is a graph showing the results ofevaluating voltage-current characteristics with respect to lightincident angle higher than critical angle, and FIG. 2c is a graphshowing the results of evaluating voltage-current characteristics withrespect to light incident angle lower than critical angle. FIGS. 2b and2c show memristor characteristics and resistor characteristics,respectively, which can be reversibly obtained depending on the changeof incident angle.

FIG. 3 is a digital circuit diagram showing that the route of light ischanged depending on the incident angle thereof, and thus twocharacteristics, that is, memristor characteristics and resistorcharacteristics are reversibly represented in the same electronicdevice, and includes schematic views showing that the changes incharacteristics of the electronic device can be obtained by the changein gradient of the electronic device or the relative position thereofwhen the angle of a light source is fixed.

FIG. 4 presents graphs showing the results of evaluating the electricalcharacteristics of the electronic device, which are repeatedly andstably exhibited in water, wherein FIG. 4a shows that the processvoltage according to the change in incident angle is reversiblyrepresented in a stable range, and FIG. 4b shows that the cumulativeprobability of current extracted from the same voltage increases underthe condition of a predetermined light incident angle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The objects, features and advantages of the present invention will bemore clearly understood from the following detailed description of thepreferred embodiments taken in conjunction with the accompanyingdrawings.

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the attached drawings.

[Embodiment 1] Combination of Electric Device Structure and Light AngleControl Technology

A device having a simple metal-insulator-metal (MIM) structure wassuperhydrophobically surface-treated to realize a structure in which airlayers are accumulated in water, thus obtaining device characteristicschanged depending on the incident angle of a light source. For thispurpose, a zinc oxide thin film, used as a semiconductor layer having aMIM structure, was grown to a thickness of 30 to 40 nm on a glasssubstrate (surface resistance: 60 Ω/cm², manufactured by AldrichCorporation) coated with a transparent indium-doped tin oxide electrodefor 5 min using RF sputtering under the conditions of a power of 50 W, apressure of 8 mtorr and room temperature. An ITO electrode was used as alower electrode having a MIM structure, and a gold electrode was used asan upper electrode. The ITO electrode and the gold electrode werepatterned using a shadow mask through thermal evaporation.

The glass substrate provided with a MIM structure was immersed into amixed solution of an aqueous 10 Mm Zn(NO₃)₂.6H₂O (purity: 98%) solutionand 1 Ml of an aqueous ammonia solution (percent concentration: 28%) for2 hours at 95° C. After zinc oxide nanowires were grown, the glasssubstrate was washed with deionized water and then dried by blowingnitrogen (N₂).

In order to coat the surface of the zinc oxide nanowires with fluorineresin, a solution containingpoly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene]was applied onto the surface thereof for 30 seconds at a spinning rateof 500 rpm and for 30 seconds at a spinning rate of 2000 rpm by spincoating, and was then dried on a hot plate for 10 min at 50° C. Thisprocedure was repeatedly carried out five times. When the zinc oxidenanowires are coated with the fluorine compound, the tips of a fluorineresin material are exposed to the surface of the zinc oxide nanowires.Therefore, water droplets are likely to stand at the tips of thenanowires, and the surface of the nanowires becomes a superhydrophobicsurface.

FIG. 1a presents photographs showing the difference in wettabilitybetween a surface-treated device and a non-surface-treated device, FIG.1b shows the lateral scanning electron microscope (SEM) images ofnonowires existing on the surface of the device, and FIG. 1c shows theplanar scanning electron microscope (SEM) images of nonowires existingon the surface of the device. As shown in FIG. 1, zinc oxide nanowireswere formed on two ITO glass substrates in the same manner to preparetwo electronic devices, and one electronic device (upper portion of FIG.1a ) was superhydrophobically surface-treated and the other electronicdevice (lower portion of FIG. 1a ) was not superhydrophobicallysurface-treated. Comparing the two devices, they were disposed at thesame angle and partially immersed into water, and then their gradientswere gradually changed. Here, the non-surface-treated device was wetbecause a boundary did not exist on the interface making contact withwater, whereas the surface-treated device is configured such thatnanowires are provided on the surface thereof with an air layer due tosuperhydrophobicity when this device was immersed in water. In thesurface-treated device, owing to the difference in refractive indexbetween the air layer and water, the appearance of the transmitteddevice is seen at a view angle below critical angle, whereas a mirrorimage is seen at a view angle above critical angle through a totalreflection phenomenon (refer to {circle around (3)}, {circle around(4)}). The surface structure of the fluorine resin-coated zinc oxidenanowire substrate was observed by a field emission scanning electronmicroscope (FESEM: JEOL, Model JSM 330F). As shown in FIG. 1b , ananowire had a length of about 600 nm and a diameter of about nm. Whenthe length of a nanowire increases, superhydrophobiity is improved, buttransparency is deteriorated because light is scattered by nanowires.Therefore, for the purpose of improving transparency, nanowires havingan optimum length of about 600 nm were synthesized.

[Embodiment 2] Realization of Memory Device Using Light Angle ControlTechnology

A light angle control technology was applied to a resistive switchingmemory device. FIG. 2 shows the refraction angle and direction of alight source and the characteristics of a resistive switching memorydevice when a superhydrophobically surface-treated electronic device isimmersed in water.

As shown in FIG. 2a , the characteristics of the resistive switchingmemory device are evaluated by connecting the lower electrode (ITO) andupper electrode (Au) of the resistive switching memory device with aplatinum probe connected to a probe station (E5270A, Agilent Inc.) toapply a voltage. In order to evaluate the reaction characteristics ofthe resistive switching memory to a light incident angle, the totalprocess was performed in water, and simultaneously, the change inelectrical performance of the resistive switching memory was observed byadjusting the angle of a light source.

FIGS. 2b and 2c show voltage-current characteristics. FIG. 2b shows thevoltage-current characteristics occurring when light is applied at anincident angle of 60° higher than the critical angle. From FIG. 2b , itcan be ascertained that the green graph occurring when voltage wascontinuously changed from −5V to +5V (when forward bias was applied) isnearly identical to the orange-colored graph occurring when reverse biaswas applied from +5V to −5V. This means that the applied voltage actedas a general resistor without exerting an influence on the position ofan energy band or the movement of an internal carrier. Meanwhile, FIG.2c is a graph showing the voltage-current characteristics occurring whenlight is applied at an incident angle of 10° lower than the criticalangle, and shows the characteristics of a resistive switching memorydevice (memristor). As shown in FIG. 2c , it is observed that the flowrate of current rapidly increases when a voltage of 4V or more isapplied to the device in the early stage. This first procedure isdefined as “forming”. Through this first procedure, the state of thedevice is converted into a low resistance state (hereinafter, referredto as “LRS”) having a low resistance value. It is observed (blue line)that the flow rate of current decreases at a voltage of about −2V whennegative voltage is further applied to the LRS device. This procedure isdefined as “reset”. Through this procedure, the state of the device isconverted into a high resistance state (hereinafter, referred to as“HRS”) having a high resistance value. When positive voltage is furtherapplied to the HRS device, the flow rate of current increases again at avoltage of about 2V, which is still lower than the initial formingvoltage. This procedure is defined as “set”. From the second circulationprocedure, voltage is applied through the set and reset procedures, andthus the resistance of a predetermined resistive switching material isreversibly changed from LRS to HRS. This characteristic is generallycalled “resistive switching characteristic”.

From the results, it can be seen that two different electricalcharacteristic of the device are reversibly changed depending on thechange in incident angle of a light source. FIG. 3 shows a digitalcircuit diagram indicating that the route of light is changed dependingon the incident angle thereof and thus two different characteristics ofthe same device, that is, a resistive memory (memristor) characteristicand a resistive (resistor) characteristic are reversibly changed. FIG. 3is a schematic view showing that the changes in characteristics of thedevice can be obtained by the change in gradient of the device when theangle of a light source is fixed, and FIG. 3 is a schematic viewexpressing the conception that the front and rear of the critical anglecan be distinguished according to the three-dimensional position of thedevice even when the relative position of the device is changed on asemicircle.

It can be ascertained that the above-mentioned characteristics of thedevice are exhibited repeatedly and stably even though a series ofprocedures are performed in water. In FIG. 4, the Y axis means anapplied voltage (Hereinafter, referred to as “process voltage”) forreaching a current of 0.01 A or a current of −0.01 A. When the angle ofthe device is set to 10° (blue, red point) and 60° (green,orange-colored point) on the X axis each time and then the processvoltages of the device, sequentially obtained from the resistiveswitching memory (memristor) and the resistor, are monitored every time,it can be seen that each of the process voltage values exists in apredetermined range. Thus, it can be ascertained that the deviceoperates according to incident light angle without departing frominherent characteristics. Further, in FIG. 4b , when probabilities arearranged in ascending powers based on the current value obtained fromeach system, it can be clearly ascertained that current characteristicsare converged, not diverged.

As described above, according to the present invention, there isprovided a method of providing light incident angle dependency by asimple procedure of accumulating additional media in various electronicdevices. In the method, the light incident angle selectivity of theelectronic device can be maintained even when the inclination angle ofthe device is changed depending on the axis parallel to the incidentdirection of light even though the incident direction thereof is fixed.This means that the performance of the device can be controlled only bychanging the inclination angle of the device without greatly changingthe dynamic state of the device. Further, since the movement speed ofphotons is higher than that of electrons and the signal interference ofphotons is lower than that of electrons, an additional effect ofincreasing the operating speed of the device or decreasing the size ofthe device can be expected.

Further, according to the present invention, optical reactivity,particularly, incident angle selectivity can be provided to variousconventional electronic devices only by post treatment, and theelectronic device of the present invention can become a key for rapidlyadvancing an information processing technology together with a typicalelectronic circuit infrastructure.

Although the embodiments of the present invention have been disclosedfor illustrative purposes, it will be appreciated that the presentinvention is not limited thereto, and those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the invention.Accordingly, any and all modifications, variations or equivalentarrangements should be considered to be within the

1. A method of changing characteristics of an electronic device,comprising the steps of: applying light to an electronic device topenetrate a plurality of transparent media having different refractiveindexes from each other, the electrical characteristics of theelectronic device being changed depending on the amount of incidentlight; and changing an incident angle of light applied to the electronicdevice to adjust the amount of incident light.
 2. The method of claim 1,wherein a first medium having a first refractive index is disposed onthe surface of the electronic device, and the light penetrates a secondmedium having a second refractive index larger than the first refractiveindex and then penetrates the first medium disposed on the surface ofthe electronic device to allow the light to be applied to the electronicdevice.
 3. The method of claim 2, wherein the first medium includes gas.4. The method of claim 3, wherein the first medium is a hydrophobiclayer including gas.
 5. The method of claim 2, wherein the first mediumis a hydrophobic layer including a nanostructure treated with fattyacid, an SAM material or a compound having low surface energy.
 6. Themethod of claim 5, wherein the compound having low surface energy is afluorine compound.
 7. The method of claim 5, wherein the nanostructureis a nanowire, nanotube or nanorod disposed on the surface of theelectronic device.
 8. The method of claim 5, wherein the nanostructureincludes at least one ingredient selected from the group consisting ofAl₂O₃, SiO₂, TiO₂, VO, VO₂, V₂O₃, V₂O₅, MnO, MnO₂, FeO, Fe₂O₃, Fe₃O₄,CoO, Co₂O₃, Co₃O₄, NiO, CuO, Cu₂O, Y₂O₃, ZrO₂, NbO, NbO₂, Nb₂O₅, MoO₂,MoO₃, RuO₂, PdO, AgO, CdO, In₂O₃, SnO, SnO₂, Sb₂O₃, Sb₂O₅, HfO₂, Ta₂O₅,WO₃, IrO₂, NiO, NO, N₂O and MgO.
 9. The method of claim 2, wherein thesecond medium is a liquid.
 10. The method of claim 9, wherein the liquidis water.
 11. The method of claim 1, wherein the light is emitted from alight source selected from the group consisting of an incandescent lamp,a halogen lamp, a discharge lamp and an LED lamp.
 12. The method ofclaim 1, wherein the light is totally-reflected depending on an incidentangle.
 13. The method of claim 1, wherein the electronic device exhibitsresistor characteristics when the light is actually totally-reflected.14. The method of claim 1, wherein the electronic device exhibitsresistive memory characteristics when the light is incident on theelectronic device.
 15. The method of claim 1, wherein the incident angleis changed depending on the change in the position of a light source orthe gradient of the electronic device
 16. The method of claim 1, whereinthe characteristics of the electronic device are reversibly changed at aspecific incident angle. 17-20. (canceled)